One reason that Congress delegates legislative authority to the executive is, as Amy suggests, to allow for a greater expansion of state power. If Congress actually had to specify all the content of regulations, they just wouldn’t have the time to do as much regulating as they’d like. But I would argue that a more explanation of why Congress delegates its power is to finesse disagreements among its own members. Making trade-offs among disparate policy goals is hard work. Members of Congress would rather not make the trade-offs, especially since they will get blamed for any actual decisions they make – possibly losing votes and campaign money. So instead, they pass vague laws that claim to make satisfy everyone. Take, for example, the mandate created under the Emergency Petroleum Allocation Act (which I’ve taken from Gary C. Bryner’s book Bureaucratic Discretion):
[Issue regulations that] protected the public health, maintained public services and agricultural operations, preserved a sound and competitive petroleum industry, allocated crude oil to refiners to permit them to operate at full capacity, resulted in an equitable distribution of supplies to all parts of the country, promoted economic efficiency, and minimized economic distortion.In short, deftly palm the coin. Why should Congress make any hard decisions, when they can tell someone else to do it for them? And then, if anyone complains, just blame the administrative agency in charge.